PARENT SESSION
Poster Session #27: Nutrient Cycling I.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Nutrient uptake by Engelmann spruce and subalpine fir at two Colorado subalpine forests.

McFarlane, Karis^*,1, Yanai, Ruth¹, Lucash, Melissa¹, ¹ State University of New York, Syracuse, NY

ABSTRACT- Measurements of nutrient uptake by intact roots in the field have the potential to improve existing understanding of uptake by trees, especially considering rates for mature trees are unknown. We measured nutrient uptake by Engelmann spruce (Picea engelmanni Parry) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) at Loch Vale Watershed and Fraser Experimental Forest, Colorado, in June 2001. Fine root branches were excavated, left attached to the tree, and exposed to nutrient solution for intervals ranging from 1 to 96 hours. The concentrations of nutrient solutions were based on reported soil solution concentrations at Loch Vale. Uptake rates for ammonium, calcium, and magnesium were consistently higher at Fraser than Loch Vale. Ammonium uptake by subalpine fir was higher than Engelmann spruce. Conversely, Ca and Mg uptake were higher in Engelmann spruce than subalpine fir. Uptake values for Fraser subalpine fir, Fraser Engelmann spruce, Loch Vale subalpine fir, and Loch Vale Engelmann spruce were 0.39, 1.2, 0.14, and 0.03 mg/g root/hr respectively for NH4; 12, 6.4, 2.7, and 0.84 mg/g root/hr for Ca; and 1.5, 1.0, 0.23, and 0.37 mg/g root/hr for Mg. Uptake of aluminum was observed for both species at Loch Vale and was calculated at 0.05 for subalpine fir, and 0.15 mg/g root/hr for Engelmann spruce. Fraser is more nutrient limited than Loch Vale, which may explain the differences in uptake between sites.

KEY WORDS: nutrient uptake, calcium, ammonium, magnesium